Magnetic alloy



Patented Jan. 31, 1933 UNITED STATES PATENT OFFICE WILLO'UGHBY STATHAM SMITH, OF NEWTON POPPLEFORD, HENRY JOSE PH GARNETT, 0F SEVENOAKS, AND WALTER FREDERICK RANDALL, OF EWELL, ENGLAND MAGNETIC ALLOY Ho Drawing. Application filed February 3, 1932, Serial No. 590,777, and in Great Britain February 5, 1931.

Per cent Nickel 62-75 Tron 1022 and from 1020% of an element to increase the specific resistance. As the resistance element any one or more of the following ele ments may be selected :--chromium, molybdenum, tungsten, vanadium, zirconium, titanium.

Amounts of up to about 1% of manganese, reckoned on the final alloy, may be added to promote forgeability.

Copper may also be added to the alloys of this invention since its presence tends to stabilize the magnetic properties, rendering them less susceptible to variations in the heattreatment and rates of cooling. About 5% of copper may conveniently be added and when copper is present, the maximum nickel and iron contents are reduced to 72% and 20%, respectively.

The alloys should be substantially free from carbon, and should be prepared by melting together the purest commercial grades of the constituent ingredients, e. g. Swedish charcoal iron, Mond nickel, chromium as sold under the registered trade mark Thermit and electrolytic copper under such conditions, that contamination is avoided e. g. in an electric induction furnace.

Alloys in accordance with the invention have an almost constant permeability and very low hysteresis losses in magnetic fields ranging from Zero up to about 1 gauss, and a high specific resistance. The initial permeability may be varied from quite low values up to about 400 by varying the nature of the resistance increasing element and the proportion thereof in the alloy, while the specific resistance is high for all the compositions.

In order to develop these desired magnetic properties, the alloys should be subjected to a heat treatment consisting in heating them at 1100 C. for 10 minutes, followed by rapid cooling. The heat treatment should preferably be carried out in a non-oxidizing atwhen forged, drawn to fine wire, annealed at 1100 C. and tested in coil form, yielded the following results 1 n ina m9 5 7 1 5.-. 9 0 147 I57 12% The specific resistance was 115 microhms per em Example 2 An alloy comprising Percent Nickel 67 .0 Iron 15.0 Copper 5.0 Chromium 12.5 Manganese 0.5

were obtained H=O. 1 n 2 O. 3-... O. 4 0. 8 gaum The specific resistance was 109 microhms per cm.

and nickel the remainder, when forged, drawn to fine wire, annealed at 1100 and tested in coil-form, yielded the following re sults a had the constant value of 180 from H=O to H=0.03.

The specific resistance was 112 microhms per cm.

Ewample,

An alloy comprising Per cent Chromium 12.0 Iron 20.0 Copper 5.0 Manganese 0.5

and nickel the remainder, when forged, drawn to fine wire, annealed at 1100 C. and tested in coil form, yielded the following results:

1. had the constant value of 390 from H=0 to H=0.07.

The specific resistance was 115 microhms per cm Ewample 5 An alloy comprising :1--

Per cent Molybdenum 10.0 Iron 15.0 Copper 5.0 Manganese 0.5

and nickel the remainder, when forged, drawn to fine wire, annealed at 1000 C. and tested in coil form, yielded the following results The same'alloy when annealed at 1100 C. yielded the following results E mample 6 An alloy suitable for dust cores comprises Ni 65%, Fe 15%, tungsten 20%.

Owing to their constant permeability, low hysteresis losses and high specific resistance, the alloys of this invention are particularly suitable for the manufacture of the cores of coils for lump-loading telephone circuits and can also be used for the continuous loading of electric conductors.

What we claim is 1. Magnetic substantially carbon free nickel iron alloys, comprising nickel 62-75%, iron 1022%, and 10-20% of a third element selected from the group comprising chromium, molybdenum, tungsten, vanadium, zirconium, titanium.

2. Magnetic substantially carbon free nickel iron alloys comprising nickel 62-72%, iron not more than 20%, 1020% of an element selected to increase the resistivity and about 5% of copper.

3. Magnetic substantially carbon free 91- loys comprising nickel about 69%, iron about 16% and about 15% of an element selected to increase the resistivity.

4:. Magnetic alloys as claimed in claim 2, with the addition of about 1% of manganese to promote forgeability.

5. Magnetic nickel iron alloys comprising nickel 62-72%, iron not more than 20%, 1020% of an element from the group comprising chromium, molybdenum, tungsten, vanadium, zirconium and titanium, and about 5% copper.

6. Magnetic substantially carbon free alloys comprising nickel about 69%, iron about 16% and about 15% of chromium.

7. Magnetic substantially carbon free nickel iron alloys comprising nickel 62-75%, iron 10-22% and 11-20% of a third element selected from the group comprising chromium, molybdenum, tungsten, vanadium, zirconium, titanium, which alloys have been subjected to a heat treatment and at a temperature and for a period suflicient to anneal the alloy completely followed by rapid cooling whereby they develop an initial magnetic permeability below 500 and which does not substantially carbon freevary more than 20% in fields up to 0.1 gauss. 8. Magnetic substantially carbon free nickel iron alloys comprising nickel 62-75%, iron not more than 22%, an& not less than 11% nor more than 20% of a third element selected from the group comprising chromium, molybdenum, tungsten, vanadium, zirconium and titanium.

In testimony that we claim the foregoing as our invention we have signed our names this 21st day of January, 1932.

WILLOUGHBY STATHAM SMITH. HENRY JOSEPH GARNETT.

WALTER FREDERICK RANDALL. 

